Brimonidine tartrate is a selective and potent alpha-2 adrenergic agonist. Brimonidine lowers intraocular pressure by reducing aqueous humor production and increasing uveoscleral outflow. Timolol maleate is a non-selective beta adrenergic receptor blocking agent. Currently marketed brimonidine and timolol combination ophthalmic solution with preservative is indicated for the reduction of elevated intraocular pressure (IOP) in patients with glaucoma or ocular hypertension who require adjunctive or replacement therapy due to inadequately controlled IOP.
Use of preservative containing eye drops has been implicated in the development or worsening of ocular surface disease. Management of open angle glaucoma and ocular hypertension require long term treatment with eye drops containing preservatives. Symptoms and signs of ocular surface disease such as ocular surface breakdown, irritation, burning, foreign body sensation, dryness, inadequate quantity of tears, etc. are prevalent in a large proportion of patients with open angle glaucoma and ocular hypertension.
Compared to eye drops preserved with benzalkonium chloride, preservative-free eye drops induce significantly fewer ocular symptoms and signs of irritation in patients, such as pain or discomfort, hyperemia, foreign body sensation, stinging or burning, and dry eye sensation.
Patients experiencing hypersensitivity reactions with benzalkonium chloride cannot use a commercial brimonidine and timolol products containing benzalkonium chloride which is preserved even with 0.005% w/v benzalkonium chloride. Benzalkonium chloride also may be absorbed by the soft contact lenses therefore patients wearing soft contact lenses are advised to remove lenses prior to administration and wait at least 15 minutes before reinserting them.